Technical Field
The present invention relates to a surveying technique.
Background Art
A technique for obtaining a three-dimensional model of the topography of an object based on image data (three-dimensional topographic data in which the topography of the object is modeled as electronic data) is publicly known (for example, refer to Japanese Unexamined Patent Application Laid-Open No. 2013-096745). The image data may be obtained by photographing a civil engineering worksite or the like from the air, for example. In this technique, work is required to add actual dimensions to the obtained three-dimensional model. In this work, reference points included in each of several tens of, to several hundreds of, or even more, still images need to be found and be matched with others among the still images.
A technique for automatically detecting the reference points by software processing has also been researched. In this technique, a step of attaching a target, which records readable positional information, on a reference point is performed so as to easily detect the reference point by software processing. However, the photographed areas in the images that were photographed from the air are vast, and therefore, the processing for automatically detecting the targets from the images and further reading the positional information takes time, and the targets tend not to be detected or to be mistakenly detected. Therefore, in actual practice, an operator needs to visually monitor the still images by manually expanding or reducing each of the still images one by one and identify the positions of targets in the still images. This working procedure should be performed on each of several tens of, to several hundreds of, or more, still images, and this is thereby complicated and inefficient.